by Dannyel Cardoso da Fonseca
This project aims to explore a data set containing 22125 observations of issues tracking and their history logs. The data set represents 5 years of project management which aimed maintenance and customization of many integrated systems (SIG) for the academic, administrative and human resources management at the Universidade Federal de Goiás (UFG).
A proprietary issue tracking system (SIGProject) was used to manage activities of company (ESIG) and client (Cercomp) teams.
I used data wrangling techniques to export data from that and clean them. The final data set, used in this project, and its documentation can be accessed, respectively, in these links:
The exported data set, the wrangling process scripts and an example of one issue tracking can be find in data_wrangling folder.
In this section, I perform a univariate exploration in the data set, by first examining the structure, followed by analysis of time series variables and ending with the analysis categorical and range variables.
The issues data set contains 22125 rows and 24 variables. Of these 24 variables 16 are about issue data and 8 about issue’s logs.
## 'data.frame': 22125 obs. of 24 variables:
## $ issue_id : int 487247 487247 ...
## $ issue_number : int 88374 88374 ...
## $ issue_title : chr "Tarefa 88374 - Alteração de Finan"| __truncated__ ...
## $ issue_type : Factor w/ 4 levels "CUSTOMIZATION",..: 1 1 ...
## $ issue_creation_date : POSIXct, format: "2016-12-15 15:07:32" ...
## $ issue_system : Factor w/ 10 levels "INDEFINIDO","SERVICOS INTEGRADOS",..: 4 4 ...
## $ issue_start_date : Date, format: "2016-12-20" ...
## $ issue_subsystem : Factor w/ 77 levels "ADMINISTRAÇÃO",..: 34 34 ...
## $ issue_deadline_date : Date, format: "2017-01-03" ...
## $ issue_created_by : chr "HELENA CLAUDIA DOS SANTOS TEIXEIRA" ...
## $ issue_stakeholder : Factor w/ 2 levels "COMPANY","CUSTOMER": 1 1 ...
## $ issue_status : Factor w/ 10 levels "CANCELED","CUSTOMER CLOSING PENDING",..: 3 3 ...
## $ issue_time_spent : int 360 360 ...
## $ issue_priority_number: int 999 999 ...
## $ issue_progress : int 100 100 ...
## $ issue_priority_scale : Factor w/ 6 levels "SUSPENDED","LOW",..: 4 4 ...
## $ log_build_info : chr NA ...
## $ log_creation_date : POSIXct, format: "2017-04-10 17:07:00" ...
## $ log_action : Factor w/ 14 levels "CHANGE OF RESPONSIBILITY",..: 5 12 ...
## $ log_status : Factor w/ 34 levels "AUTHORIZED DEVELOPMENT",..: 7 4 ...
## $ log_progress : int 100 100 ...
## $ log_time_spent : int NA NA ...
## $ log_created_by : chr "ROSANGELA DIVINA DE SOUSA SANTANA" ...
## $ log_svn_revision : int NA NA ...
The number of distinct issues rows and issue’s logs rows are 4503 and 21978 respectively. That is, the number of issues represents 20% of the data set and the number of logs represents 99% of it. The 1% of logs remaining (147 rows) represents issues that do not have history logs.
The distribution and the summaries of number of logs per issue are ploted in the histogram below.
Note: In the plot above, the black dashed lines represent the 1st and 3rd quartile, the black and red solid lines represent, respectivaly, median and mean, the red shading represents the 95% of mean confidence interval (not visible in this plot because its narrow interval) and the black dotted line represent the upper threshold to the outliers (3rd qu. + 1.5 IQR).
Analysing the plot above, we can note that most of issues have between 1 and 9 history logs (1 standard deviation from the mean), 75% of them have up to 6 history logs and 50% of issues have between 2 and 6 logs, a narrow range. Despite the skewed shape of plot, the median and mean are very close. This means that the amount of ouliers (after 12 logs per issue) is very low, approximately 4% of issues.
The representative narrow range of logs in an issue makes us think that there shoud be an activity flow pattern to resolve an issue. This flow pattern migth be observed in a commom sequence of log status. See more informations in the Log Status section.
The next 6 sections show the analisys of the temporal variables: four originally in the data set (issue_creation_date, issue_start_date, issue_deadline_date and issue_time_spent) and two derived from the calculation (issue_delay_start and issue_deadline_size). In an issue tracking system, temporal variables is the fundamental piece for monitoring and control of activities.
The data set analyzed comprises issues created in the period between 05/21/2013 and 01/26/2018. More precisaly, between 19:10:24 of 05/21/2013 and 16:16:06 of 01/26/2018.
To get a sense of how it was the demand throughout the project see the plot below that shows the cumulative number of issues created per month along the project and its trend line.
Note: In the plot above, the blue solid line represents the trend of the data and solid grey vertical lines represent the 1st day of year.
We note that the first 11 months (from May 2013 to March 2014) of the project had very low demand, approximately 4% of the total. Some reasons for this were:
The work processes and knowledge on both sides (customer and company) were being built over those 11 months. The teams grew in size and new modules started development and deployment. The next 12 months (from April 2014 to March 2015) there was significant growth curve in the activities, approximately 25% of growth over the previous 11 months. From June 2015 the activities growth seems to stabilize, sometimes taking small growth curves. In this period occurred approximately 65% of project activities. Besides, the trend line fitted with growth curve demonstrating that the project began to have a standardized behavior.
In the area plot below, we can see the project’s behavior in another way. This plot shows the distribution of the number of issues created per month and their cumulative summaries.
Note: In the plot above, the black dashed lines represent the 1st and 3rd cumulated quartile, the black and red solid lines represent, respectivaly, cumulated median and mean, the red shading represents the 95% of cumulated mean confidence interval and solid grey vertical lines represent the 1st day of year.
Analysing the area plot above, we note that the year 2013 had the lowest demand. The cumulated mean variates around 15 issues per month. At the end of 2013 and begin of 2014 there was a drop in activities because of the low administrative and academic activities at the university at the end of year.
From April of 2014 until February of 2015 there was significant growth in activities. The cumulated mean increases from 15 to 50 issues per month and it overcame the cumulated median. The distance between cumulated 3rd quartile and cumulated median became greater than distance between cumulated 1st quartile and cumulated median. The 95% of cumulated mean confidence interval also increases indicating an increase in the variability in the data history. All this indicates that these months had a high number of issues created in relation to the past.
But from August of 2015 the pace of growth dropped. Now, we can note that the distance between cumulated 1st quartile and cumulated median becomes greater than distance between cumulated 3rd quartile and cumulated median. This invertion provocated the overlap between cumulated mean and median. The stabilization of the growth also contributed to that. The average of growth pass to be only 10 monthly issues (from 70 to 80), approximately.
We also note that except the significant growth period (from April 2014 to February 2015) the months between September and December of each year had a decline in activities. The reason is the low administrative and academic activities at the university in this period. Thus, the demand for customization and maintenance of the systems decreases.
During the week, the demand for new activities were concentrated on business days (from Monday to Friday) as we can note in the barplot below.
Note: In the plot above, the black dashed lines represent the 1st and 3rd quartile, the black and red solid lines represent, respectivaly, median and mean and the red shading represents the 95% of mean confidence interval.
Note that whether we sort business days by the frequency of issue creations we have Tue > Wed > Thu > Fri > Mon. Tuesday is the weekday that has more issues creation (mode). Monday and Friday are the business days with less issues creation. One of the reasons for this is that, from April 2014, the work began to be planned by sprints. These sprints were planned every Tuesday morning and issues were created in the afternoon.
Issues created on weenkend (18 issues) may be considered outliers. These are issues created on weekend shift that was done during the enrollment periods. Theses outliers pull the mean and 1st quartile down, increase the standard deviation and the 95% of mean confidence interval. Removing them, we have a new barplot. See it below.
Note: In the plot above, the black dashed lines represent the 1st and 3rd quartile, the black and red solid lines represent, respectivaly, median and mean and the red shading represents the 95% of mean confidence interval.
Note that the summaries are now approximated. The median and mean overlap, the distance between 1st and 3rd quartile became narrow, the standard deviation and the 95% of mean confidence interval descrease. These new summaries better reflect the behavior of issue creation.
Analysing how was the behaviour of the issue creations per hour of the day we have the bimodal distribution below.
Note: In the plot above, the black dashed lines represent the 1st and 3rd quartile, the black and red solid lines represent, respectivaly, median and mean, the red shading represents the 95% of mean confidence interval and the black dotted lines represent the lower and upper threshold to the outliers (lower = 1st qu. - 1.5 IQR, upper = 3rd qu. + 1.5 IQR).
The high volume of issue creation comprises between 8:00h and 18:00h, office hours. The peak hours are around 10:00h and 15:00h. At lunch time, the demand for new issues decreases. We note that this bimodal distribution is quasi symmetrical. The 1st and 3rd quartiles match with modes and the median and mean differ by a few minutes.
Ploting this distribution again but with only office hours (from 8:00h to 18:00h) we have the same summaries of the distribution before. See the plot below.
Note: In the plot above, the black dashed lines represent the 1st and 3rd quartile, the black and red solid lines represent, respectivaly, median and mean and the red shading represents the 95% of mean confidence interval.
This shows us that the high issue creation volume actually comprises between 8:00h and 18:00h.
The behavior of the project in relation to the starting of a issue activity is similar to the behavior of its creation. The main differences are that the creation date has time information while start date does not have and there are more observation of creation date than start date.
To show how is similar the behavior between creation and start issue date see the cumulative number of issues started along the project and its trend line in the plot below.
Note: In the plot above, the blue solid line represents the trend of the data and solid grey vertical lines represent the 1st day of year.
Pratically it has the same shape and values of the Cumulative Number of Issues Created per Month plot.
This similarity induces us to believe that there was not a big delay between the creation and the starting of a issue. To verify this, I created a new variable named issue_delay_start which represents the delay, in calendar days, between creation of an issue and its start.
See in the plot below the distribution of the delay between creation and start date.
Note: In the plot above, the black dashed lines represent the 1st and 3rd quartile, the black and red solid lines represent, respectivaly, median and mean, the red shading represents the 95% of mean confidence interval and the black dotted lines represents the upper threshold to the outliers (3rd qu. + 1.5 IQR).
About 80% of 4478 issues, with start date information, have less than or equal 5 calendar days of delay to start. These amount of days is very short compared to the 30 days of the month (granularity used in the plots).
Note also that 95% of the mean confidence interval is very narrow even though the standard deviation to be high and the dataset contain outliers with high number of calendar days. This indicates that the affirmative of the previous paragraph is robust.
Issue deadline date represents the planning date to deliver the issue. It is planned at the beginning (start) of the activities to solution an issue.
It seems to follow the same behaviour that issue creation and start date but it has some particularities, starting by amount of NA values. Issue deadline date has more NA values than those, approximately 67% of the number of issues.
Its cumulative plot is also a bit different from the others. See the plot below.
Note: In the plot above, the blue solid line represents the trend of the data and solid grey vertical lines represent the 1st day of year.
Until January of 2017, the growth curve of the cumulative number of issues deadlines per month is similiar to the creation and start growth curve. After that, a fall happens. Because that, the trend line does not fit well with growth curve.
In the plot below, we can see this behavior in another way.
Note: In the plot above, the black dashed lines represent the 1st and 3rd cumulated quartile, the black and red solid lines represent, respectivaly, cumulated median and mean, the red shading represents the 95% of cumulated mean confidence interval and solid grey vertical lines represent the 1st day of year.
Note how, after April of 2017, the frequency of issue deadlines decreases and does not rise again. The same occur with cumulated summaries. This phenomenon did not occur with creation and start date.
The reason for this is lack of data. After April of 2017, the number of issues with deadline information decreases. Few issues have planned your delivery date. This is interesting information for teams to review in order to improve planning and control of activities.
As expected, issue deadlines do not occur on Sundays. The deliver was planned to business days (from Monday to Friday) as we can note in the barplot below.
Note: In the plot above, the black dashed lines represent the 1st and 3rd quartile, the black and red solid lines represent, respectivaly, median and mean, the red shading represents the 95% of mean confidence interval and the black dotted lines represents the upper threshold to the outliers (3rd qu. + 1.5 IQR).
Issues with deadline to weenkend may be considered outliers. These are issues created on weekend shift (during the enrollment periods) with deadline size 0 (day). Removing them, we have a new barplot. See it below.
Note: In the plot above, the black dashed lines represent the 1st and 3rd quartile, the black and red solid lines represent, respectivaly, median and mean, and the red shading represents the 95% of mean confidence interval.
Tuesday is the weekday that has more issue deadlines (mode). Monday and Friday are the business days with less issue deadline. The reason for this is similar to issue creation and start date: from April 2014, the work began to be planned by sprints and these sprints were planned every Tuesday morning. The sprints had one week duration and, for a time, had two weeks duration. Always starting and ending on Tuesdays. It is worth mentioning that not all issues were part of the sprint and not all issues in the sprint had deadline of the sprint size.
The issue deadline size represents the total planned time to solve and deliver an issue, that is, the difference between issue start and deadline date. This variable is interesting because it gives us an idea of the planning of the activities.
See in the plot below how is the distribution of the deadline size.
Note: In the plot above, the black dashed lines represent the 1st and 3rd quartile, the black and red solid lines represent, respectivaly, median and mean and the black dotted line represents upper threshold to the outliers (3rd qu. + 1.5 IQR).
Note that the common planning is to solve issues and deliver them within 7 days or exactly in 14 days. The most issues are planned to deliver in the same day. These issues should be easy to resolve or have high priority.
The reason for some issues have 14 days of deadline size is had a period in the project that there were two weeks sprints. But this planning was later changed to one week sprints.
## min qu1 median mean mean.ci.low mean.ci.high mean.se sd qu3
## x 0 0 0.5 2.205639 2.046354 2.370141 0.08295759 5.57809 2.1
## iqr max
## x 2.1 107.4
## min qu1 median mean mean.ci.low mean.ci.high mean.se sd qu3
## x 0 0 0 10.87472 10.30425 11.4519 0.2948627 15.25582 18
## iqr max
## x 18 54
## issue_time_spent score
## 1 0 1430
## 2 6 242
## 3 12 241
## 4 30 187
## 5 18 174
## min qu1 median mean mean.ci.low mean.ci.high mean.se sd qu3
## x 6 12 18 23.29553 22.48574 24.09105 0.4081639 14.46379 36
## iqr max
## x 24 54
## min qu1 median mean mean.ci.low mean.ci.high mean.se sd qu3
## x 0.1 0.5 1.3 3.232018 3.016829 3.467646 0.1159698 6.502356 3.4
## iqr max
## x 2.9 107.4
In the issue tracking system, 4 types of issues were used to classify the purpose of a issue. They are:
## [1] "CUSTOMIZATION" "DATA MIGRATION" "MAINTENANCE" "OTHERS"
The frequency of issues created by each issue type is shown in the graph below.
Analysing the plot above, we note that most of the issues are of the MAINTENANCE type (around 75%). Next comes the issues of the CUSTOMIZATION type (around 20%). And, with less than 0.05% comes the issues of the types DATA MIGRATION and OTHERS. Thus, we can summarize that project management was characterized by corrective maintenance activities of existing systems and subsystems.
The demand for adaptation and evolution of the systems was not insignificant. Although the amount of CUSTOMIZATION and DATA MIGRATION issues are less than MAINTENANCE, they may have indirectly influenced in the creation of large volume of MAINTENANCE issues. Maybe, CUSTOMIZATION issues had provocated related creation of MAINTENANCE issues. The same is true for DATA MIGRATION. An analysis of issue creations timeline by system/subsystem may answer that assumption.
## issue_priority_number score
## 1 999 2272
## 2 0 427
## 3 1 243
## 4 2 192
## 5 3 148
## issue_progress score
## 1 100 4492
## 2 0 8
## 3 50 1
## 4 60 1
## 5 90 1
Go back: Data Set Structure
What is the commom flow of the log states? (Data Set Structure)
What makes the demand low in 2013? What makes the demand grow rapidly in 2014?